Programmed digital to analog function generator motor control for an x-y plotter



Nov. 9, 1965 w. J. MULDOON 3,217,219 PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER Filed Dec. 29, 1961 19 S s-Sheet l C? a( W ,4 /5-i/ 0 ,5 .L z o 772 7 [dz] 0 72 7 W z zaa,

William J. Muldoon,

INVENTOR.

AGENT.

Nov. 9, 1965 w. J. MULDOON 3,217,219

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PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER Filed Dec. 29, 1961 19 Sheets-Sheet 8 Nov. 9, 1965 GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER Filed Dec. 29, 1961 19 Sheets-Sheet 9 Nov. 9, 1965 w. J. MULDOON PROGRAMMED DIGITAL TO ANALOG FUNCTION l9 Sheets-Sheet 10 Filed Dec. 29, 1961 NOV. 9, 1965 w MULDOON 3,217,219

PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER Filed Dec. 29, 1961 19 Sheets-Sheet l2 19 Sheets-Sheet 13 w. J. MULDOON FOR AN X-Y PLOTTER GENERATOR MOTOR CONTROL PROGRAMMED DIGITAL TO ANALOG FUNCTION Nov. 9, 1965 Filed Dec.

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W. J. MULDOON PROGRAMMED DIGITAL TO ANALOG FUNCTION Nov. 9, 1965 GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER 19 Sheets-Sheet 14 Filed Dec. 29, 1961 Nov. 9, 1965 w. J. MULDOON 3,217,219

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PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER Filed Dec. 29, 1961 19 Sheets-Sheet l7 m O h n n n h w u n w u I N V Y .v un M mN NN mw Q SQ vs ub H N Nov. 9, 1965 w. J. MULDOON PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER 19 Sheets-Sheet 18 Filed Dec. 29, 1961 Nov. 9, 1965 w. J. MULDOON PROGRAMMED DIGITAL TO ANALOG FUNCTION GENERATOR MOTOR CONTROL FOR AN X-Y PLOTTER 19 Sheets-Sheet 19 Filed Dec. 29, 1961 United States Patent 3 217 219 PRQGRAMMED DHGIT AL T0 ANALQG FUNCTION GENERATOR MOTUR (IUNTROL FOR AN X-Y PLOTTER William .l. Muldoon, Palos Verdes Estates, Califl, assignor to Hughes Aircraft Company, Culver City, Calif, a

corporation of Delaware Filed Dec. 29, 1961, Ser. No. 163,277 ll Claims. (Cl. 318-462) This invention relates generally to systems of electrical control, and more particularly to such systems which are capable of accurately positioning and moving an element in accordance with a predetermined instruction program.

While the descriptive-disclosure hereinafter is particularly directed to a system for moving a pen or other line drawing implement according to a specified program for the purpose of making drawings, writing, printing and the like, it will be appreciated that this invention is not particularly limited to such a specific function or to such a particular type of output device but may be used to power any suitable device in the layout or manufacture of printed circuits in machining operations, etc.

Efforts have been made by others to automatize drafting, that is, to automatize the making of line drawings. These prior art systems have been developed to the point where the specific drawing is completely encoded on a digital record member as a digital program. These systems are usually based upon a system of mathematics, defining straight lines in point-slope form. The digital program is transduced in a specific sequence and converted to analog form to power a suitable type of analog servo system having a pair of servo motors which power and move a single output member in each of two mutually perpendicular directions.

These prior art arrangements have proved satisfactory for drawing straight lines at differing slopes. They have, however, been particularly limited to the drawing of straight lines. In such systems curves have been simulated by drawing short, straight lines of progressively changing slopes in end-to-end relationship. In a system of this type, depending upon how accurately a curved line is to be simulated, the use of shorter and shorter straight line segments requires correspondingly larger numbers of definitions of line start and end points to achieve the desired approximated curve. This is a very time consuming operation from the viewpoint of preparing the program, as well as from the viewpoint of the time of operation of the machine in reading and reproducing these multitudes of short, straight line segments in simulating curves.

An object of this invention is to provide an improved position system for selectively generating both straight lines and curves.

Another object of this invention is to provide an improved system for generating lines describing geometric figures in which line generating sine and cosine voltages are combined in differing ways to selectively generate straight lines and selected curves.

It is additionally an object of this invention to provide an improved electrical control system including provisions for generating a plurality of time varying electrical quantities of differing phase and steady state electrical quantities and for combining these differing quantities in differing ways to produce an electrical quantity having a desired time varying characteristic.

A further object of this invention in a system of the character referred to is to provide respective networks for attenuating steady state and time varying voltages in terms of coordinate positions of the center of a geometric figure to be drawn and in terms of the coordinate of the starting point of the line describing the figure, respectively.

ice

With reference to the preceding object it is an object thereof to provide time varying voltages of differing phase and to combine these time varying voltages in differing Ways to generate selectively circular arcs or ellipses.

A specific object of this invention in a system of the character referred to is to provide fixed amplitude time varying voltages of the same or differing phase relationship which are attenuated in an amount proportional to the coordinates of the starting point of a line and utilized as line generating voltages.

Another specific object of this invention is to provide an improved fixed voltage and/ or variable voltage energized system of attenuating networks for producing line generating voltages.

The aforesaid and other objects and advantages are achieved in an arrangement according to this invention which generates and employs time variable electrical quantities characterized by selected time parametric functions for controlling a servo system to selectively describe straight lines, circular arcs, or circles, and elliptical arcs, or ellipses, of specific dimension or sizes and at particularly defined points in a given reference plane, such as a drawing board.

The program of the servo system is digitally encoded on a suitable record medium, such as paper tape, magnetic tape or other record bearing medium, as a discrete information code system in conventional binary code, for instance, together with other discrete information recordings having place of position significance on the medium for directing control of specific control elements in the system. Suitable transducers read this medium or tape and the signals thus generated after suitable conversion, amplification and shaping, if needed, are stored in a digital storage circuit such as a shift register which may include a plurality of flip flops conventionally set in correspondence with the respective discrete signals. The digitally encoded information includes the following:

(1) Dimensions in both coordinates from a reference point in the reference plane to the geometric center of the figure which is to be drawn.

(2) Dimensions and their signs defining the starting point of any line describing a geometric figure in terms of the respective coordinates of that point referred to the geometric center of the figure.

(3) Dimensions and their signs defining the stopping point of any line.

(4) Respective commands denoting if a circular are or an ellipse is to be drawn.

(5) Respective commands denoting which of several line thicknesses is to be used.

(6) Respective commands denoting if any of several line interruption patterns (line characteristics) is to be used.

The system includes a variable frequency electrical function generator for generating sine and cosine electrical quantities of a fixed magnitude which are relatively positive or negative depending upon the algebraic signs of the coordinates defining the starting point of the line describing the geometric figure in relation to the geometric center of the figure and which vary in frequency as a function of a selected algebraic combination of at least a portion of the information defining these coordinates to provide time varying output voltages having a frequency roughly inversely proportional to the desired length of a line.

The time varying voltages thus generated are attenuated, or amplitude modulated, or multipled by another voltage, or otherwise suitably modified, in selected pairs as a function of the coordinates of the starting point of the line defining the figure to provide simultaneous time varying X and Y line generating voltages, the corre 

1. A LINE GENERATING SYSTEM, COMPRISING: A PAIR OF SERVOS HAVING RESPECTIVE INPUT CIRCUITS AND RESPECTIVE OUTPUT MOTORS; A DEVICE INCLUDING A PAIR OF INPUT MEMBERS CONNECTED TO AND DRIVEN BY SAID MOTORS, RESPECTIVELY, AND HAVING AN OUTPUT MEMBERS CONNECTED TO AND DRIVEN BY BOTH OF SAID INPUT MEMBERS IN SUBSTANTIALLY MUTUALLY PERPENDICULAR DIRECTIONS; A GENERATOR DEVICE HAVING A SINE VOLTAGE OUTPUT CIRCUIT AND A COSINE VOLTAGE OUTPUT CIRCUIT; CIRCUIT MEANS CONNECTING SAID COSINE VOLTAGE OUTPUT CIRCUIT TO THE INPUT CIRCUIT OF ONE OF SAID SERVOS; CIRCUIT MEANS CONNECTING SAID COSINE VOLTAGE OUTPUT CIRCUIT TO THE INPUT CIRCUIT OF THE OTHER OF SAID SERVOS; NORMALLY INOPERATIVE SWITCHING MEANS FOR COUPLING, WHEN OPERATED, SAID SINE VOLTAGE OUTPUT CIRCUIT TO THE INPUT CIRCUITS OF BOTH OF SAID SERVOS; AN MEANS CONNECTED TO SAID SWITCHING MEANS TO CONTROL SAID SWITCHING MEANS BETWEEN INOPERATIVE AND OPERATIVE CONDITIONS. 